1. Field of the Invention
The present invention relates to golf balls. More particularly, the present invention relates to golf balls having a core and a cover, with dimples being formed on the cover.
2. Description of the Related Art
General golf balls that are commercially available in the market have a core and a cover. The core is composed of a solid rubber, and the cover is composed of a resin composition. There also exist golf balls having a core composed of a center and a mid layer. The mid layer may be composed of a solid rubber, or alternatively, may be composed of a resin composition.
There are numerous dimples formed on the surface of the cover. The role of the dimples involves causing turbulent flow separation by disrupting the air flow around the golf ball during flight (hereinafter, referred to as “dimple effect”). By causing the turbulent flow separation, a separating point of air from the golf ball shifts backwards leading to the reduction of a drag coefficient (Cd). The turbulent flow separation promotes the differential between upper and lower separating points of the golf ball that result from the backspin, thereby enhancing the lifting force that acts upon the golf ball. Flight distance of the golf ball is prolonged on behalf of the reduced drag and enhanced lift force. Aerodynamically, excellent dimples promote turbulent flow separation. In other words, aerodynamically, excellent dimples may provide a better air flow.
During the flight of a golf ball, the air flows along the dimples. The shape of the dimple is one of the important factors that determine the aerodynamic characteristics of the golf ball. In an attempt to improve the dimple effect, a variety of proposals have been made in connection with the cross sectional shape of the dimple. JP-A No. 2-68077 discloses dimples having a protrusion at the center. U.S. Pat. No. 5,735,757 discloses dimples having two curved faces with different curvatures.
The volume of the dimples is also one of the important factors that determine aerodynamic characteristics of a golf ball. U.S. Pat. No. 4,813,677 discloses a golf ball having a dimple volume defined as an index which falls within a predetermined range.
What are most demanded for a golf ball by golf players are flight performances. There is still an opportunity for improving dimples to enhance flight performance. Accordingly, an object of the present invention is to provide a golf ball that achieves a great flight distance.